drm/amd/powerplay: delete some dead code
We deleted some code in e154162ef75d ("drm/amd/powerplay: refine pp code
for raven") but there were a few related bits that were missed. Let's
delete them as well.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>